Abstract:

Objective: To study anti-oxidant activity of chitooligosaccharide (COS) and its protective effect against lipopolysaccharide (LPS)-induced oxidative injury in microglial cell line N9. Methods: The antioxidant activity of COS in vitro was evaluated by DPPH and hydroxyl free radical and hydrogen peroxide scavenging assays. Microglial cell line N9 was treated with LPS alone at the dose of 1 μg/mL or co-treated with LPS at the dose of 1 μg/mL and COS at doses of 50, 100, 200, 300 μg/mL and 400 μg/mL, respectively. Cell morphology was examined under microscope with HE staining and NO level in cell culture supernatant was determined. Intracellular generation of reactive oxygen species (ROS) was detected using 2',5' dichlorofluorescin diacetate (DCFH-DA) and flow cytometry combined with fluorescence microscope. Cell apoptosis was detected by DNA ladder assay. Results: COS exhibited an effective scavenging activity against DPPH and hydroxyl free radicals but no scavenging activity against H2O2. Meanwhile, COS attenuated the activation of microglial cell line N9 induced by LPS. The level of NO in cell culture supernatant was significantly decreased due to the presence of COS, and ROS generation induced by LPS was inhibited by COS in a dose-dependent manner. COS also inhibited the apoptosis of microglial cell line N9 induced by LPS. Conclusion: The antioxidant activity of COS is beneficial for protecting microglial cell line N9 from oxidative injury induced by LPS.

Key words: anti-oxidant activity, chitooligosaccharide, microglial cell, apoptosis